We present the first recorded range extension of a euryhaline invertebrate in the climate change hot-spot along Australia’s southeastern coast. The river swimming crab, Varuna litterata (Fabricius, 1798) (Varunidae) was found in the Coffs Harbour-Bellinger and Nambucca river basins of New South Wales, Australia in 2013, 2014 and 2016. The crabs were found during winter in shallow freshwater habitats, and may be using these habitats to avoid predators or minimise exposure to colder temperatures in deeper water. At locations where the crabs were found, water temperatures during winter (July 2016) were up to 4.5 °C warmer in shallow-water habitats (< 0.2 m depth) compared to adjacent deep-water habitats (> 1.0 m). The new southernmost locations of V. litterata reported here represent a ~290 km poleward range extension. The likelihood that climate change and a strengthening East Australian Current have contributed to this range extension is discussed, as well as the potential impacts of these crabs on existing biological communities in newly colonised locations.